Rear axle steering system with pressure shock protection and control method thereof

Abstract

The present invention discloses a rear axle steering system with pressure shock prevention and a control method thereof, including symmetrically arranged left and right tires, a left steering oil cylinder for outputting hydraulic power to drive the left tire to rotate, a right steering oil cylinder for outputting hydraulic power to drive the left tire to rotate, a steering valve group including a proportional valve and a back pressure valve, an oil return port T1 communicating with an oil return port T through a back pressure valve, an oil inlet P of the steering valve group communicating with a pressure oil source, an oil return port T of the steering valve group communicating with a system oil return or with an oil return port of a hydraulic oil tank, and a working oil port A and a working oil port B of the steering valve group communicating with a left steering oil cylinder and a right steering oil cylinder of a vehicle, respectively, for controlling the extension and retraction of the left steering oil cylinder and the right steering oil cylinder. The present invention improves the rigidity of the rear axle steering system by adding a back pressure valve, improves the steering stability of the vehicle when driving on a curve, and avoids the problem of tail swinging caused by excessive steering of the rear axle when the vehicle turns rapidly at high speed and with heavy load.

Description

Technical Field

[0001] The invention relates to a rear axle steering system, and in particular to a rear axle steering system with pressure shock protection and a control method thereof. Background Art

[0002] In order to improve the vehicle's maneuverability and turning ability, more and more vehicles use the rear axle as a steering axis and participate in the vehicle's steering process. When the vehicle is turning at low speed, the rear wheels steer in the opposite direction of the front wheels, and the vehicle achieves the minimum turning ability; when driving at high speed, the rear axle no longer participates in steering or turns in the same direction as the front axle, and the vehicle achieves high-speed handling stability.

[0003] Curving stability is an important evaluation content to evaluate whether the vehicle's motion trajectory is consistent with the driver's expectations when accelerating and braking in a curve, and whether there are situations such as pushing the head and swinging the tail. The turning driving characteristics of a vehicle are generally divided into three situations: understeering, neutral steering and oversteering. Understeering is manifested as the actual steering angle of the vehicle during the turning process is smaller than the theoretical turning angle, that is, the equivalent front wheel slides outward; oversteering is manifested as the actual steering angle of the vehicle during the turning process is larger than the theoretical turning angle, that is, the equivalent rear wheel slides outward; neutral steering is manifested as the actual steering angle of the vehicle during the turning process is exactly the theoretical turning angle. If the rear wheel steering is not properly controlled, the vehicle may oversteer when turning at high speed, which will seriously affect the safe driving of the vehicle and reduce the vehicle's handling stability.

[0004] In order to improve the vehicle handling stability, the existing technologies are mostly focused on the improvement of technical solutions such as steering proportional valve, steering control method, rear axle steering centering system, etc. The specific contents are as follows:

[0005] Prior art 1: Application publication number CN114852166A "Steering system and engineering vehicle" (Applicant: Sany Automobile Hoisting Machinery Co., Ltd.) provides a steering system and engineering vehicle, the steering system includes an electric proportional pump, a steering module, a control valve group, a controller, a fuel tank and a first acquisition unit; the first acquisition unit is used to obtain the target steering data of the engineering vehicle; the controller controls the electric proportional pump and the control valve group according to the target steering data, and the steering system makes it possible to accurately control the action of the steering module, which can improve the reliability of the control of the steering system. In the prior art 1, the steering proportional valve adopts a three-position four-way proportional throttle reversing valve with a middle position function of O type, and the proportional valve T port is directly led back to the hydraulic oil tank, that is, whether the proportional valve B→proportional valve T→hydraulic oil tank return oil, or the proportional valve A→proportional valve T→hydraulic oil tank return oil, the pressure of the proportional valve B and the proportional valve A in both cases is negligible. If there is a sudden load acting on the steering wheel, the steering wheel is difficult to withstand the impact load and deflects, resulting in the vehicle tail swinging or other effects on the vehicle's driving safety and handling stability.

[0006] Prior art 2: Application publication number CN102862603B "Proportional steering valve, proportional steering hydraulic circuit, proportional steering system and vehicle" (Applicant: Zoomlion Heavy Industry Science & Technology Co., Ltd.) provides a proportional reversing valve composed of a reversing valve and a proportional throttle valve, which realizes flow control function and reversing function, accelerates response speed, and improves the sensitivity of steering operation. Prior art 2 has the same problem as prior art 1. The steering proportional valve adopts a three-position four-way proportional throttle reversing valve with a mid-position function of O type, and the proportional valve T port is directly led back to the hydraulic oil tank, that is, whether proportional valve B→proportional valve T→hydraulic oil tank oil return, or proportional valve A→proportional valve T→hydraulic oil tank oil return, in both cases, the pressure of proportional valve B and proportional valve A is negligible. If a load suddenly acts on the steering wheel, the steering wheel is difficult to withstand the impact load and deflects, causing the vehicle to drift or other effects on vehicle driving safety and handling stability.

[0007] Prior art 3: Patent publication number DE10245618B4 "Aktive Hinterachslenkung Für Einen Fahrzeugkran (Active rear axle steering for truck cranes)" (Applicant: LIEBHERR-WERKEHINGEN GMBH (Liebherr) provides an active rear axle steering system for a vehicle crane with two, four, six or more paired steered rear axles, the technical solution being that the steering angle of the rear axle is electronically controlled, and the steering deflection of the rear axle is performed by a hydraulic steering cylinder; the hydraulic centering cylinder is connected to a check valve, wherein the check valve is controllable via a directional control valve so that they close in the event of a failure, so that the rear axle cannot be further deflected; the hydraulic steering cylinder and the hydraulic centering cylinder of the corresponding rear axle can be actuated by a safety valve, the safety valve acts on the centering cylinder under a given driving state, so that the associated rear axle can return to a neutral position, and the steering cylinder no longer acts on the deflected position, wherein during turning, if a change in the steering movement in the direction opposite to the previous steering movement is detected, the safety valve for returning the associated rear axle to the neutral position can be activated by a control signal. Most of the above-mentioned existing technologies focus on how to achieve precise steering of the rear axle, rear axle centering control devices and control methods, etc. The specific characteristics are that the steering proportional valve mostly uses a three-position four-way proportional throttling reversing valve, and the T port of the proportional valve is directly connected to the oil return port of the hydraulic oil tank, which generates lateral force on the rear axle. The rear axle may oversteer under the action of the centrifugal force of the vehicle body, and is prone to problems such as tailspin caused by excessive steering of the rear axle when the vehicle turns rapidly at high speed and heavy load.

[0008] Therefore, it is urgent to solve the above problems. Summary of the invention

[0009] Objective of the invention: The first objective of the present invention is to provide a rear axle steering system with improved rigidity and pressure shock resistance.

[0010] A second object of the present invention is to provide a control method for the rear axle steering system with pressure shock protection.

[0011] Technical solution: To achieve the above objectives, the present invention discloses a rear axle steering system with pressure shock protection, comprising:

[0012] Symmetrically arranged left and right tires,

[0013] The left steering cylinder is used to output hydraulic power to drive the left tire to rotate.

[0014] The right steering cylinder is used to output hydraulic power to drive the left tire to rotate.

[0015] A steering valve group having a working oil port A, a working oil port B, an oil inlet P and an oil return port T, the steering valve group including a proportional valve and a back pressure valve having a working oil port A1, a working oil port B1, an oil inlet P1 and an oil return port T1, wherein the working oil port A1 is communicated with the working oil port A, the working oil port B1 is communicated with the working oil port B, the oil inlet P1 is communicated with the oil inlet P, and the oil return port T1 is communicated with the oil return port T through the back pressure valve;

[0016] The oil inlet P of the steering valve group is connected to the pressure oil source, the oil return port T of the steering valve group is connected to the system return oil or the oil return port of the hydraulic oil tank, and the working oil port A and the working oil port B of the steering valve group are respectively connected to the left steering cylinder and the right steering cylinder of the vehicle, and are used to control the extension and retraction of the left steering cylinder and the right steering cylinder.

[0017] Among them, the back pressure valve is composed of a first one-way valve and a second one-way valve in parallel, and the opening pressure of the first one-way valve is greater than that of the second one-way valve; the oil inlet of the first one-way valve is connected with the oil return port T1 of the proportional valve, and the return oil of the proportional valve returns to the hydraulic oil tank through the first one-way valve; the oil inlet of the second one-way valve is connected with the oil return port T of the steering valve group, and the return oil of the hydraulic oil tank replenishes the oil return chamber of the proportional valve through the second one-way valve.

[0018] Preferably, the back pressure valve is composed of a relief valve and a check valve in parallel, and the return oil of the proportional valve returns to the hydraulic oil tank through the relief valve; the oil inlet of the check valve is connected to the return oil port T of the steering valve group, and the return oil of the hydraulic oil tank is replenished to the return oil chamber of the proportional valve through the check valve.

[0019] Furthermore, a pressure compensation valve is connected in series between the oil inlet P1 of the proportional valve and the oil inlet P of the steering valve group, and a throttle valve is connected in series between the flow feedback oil port of the pressure compensation valve and the oil inlet P1 of the proportional valve.

[0020] Furthermore, a first overflow valve and a third check valve are sequentially connected between the working oil port A1 of the proportional valve and the working oil port A of the steering valve group, and a second overflow valve and a fourth check valve are sequentially connected between the working oil port B1 of the proportional valve and the working oil port B of the steering valve group.

[0021] Preferably, the left tire and the right tire are respectively hinged at both ends of the wheel axle, and the two ends of the wheel axle are respectively connected to the two ends of the parallel connecting rod through the left swing arm and the right swing arm, one end of the left steering cylinder is hinged to the wheel axle, and the other end of the left steering cylinder is hinged to the middle part of the left swing arm, one end of the right steering cylinder is hinged to the wheel axle, and the other end of the right steering cylinder is hinged to the middle part of the right swing arm.

[0022] Furthermore, the rear axle steering controller is included, which obtains vehicle speed, axle 1 steering angle, and electronically controlled axle steering angle information, and when the vehicle speed increases and reaches a certain critical vehicle speed V criti_0 When the steering angle of the 1st axis as the steering reference is within a small turning angle range (-δ0, δ0), the rear axle steering controller can determine that the current vehicle has the conditions for the electronically controlled rear axle to return to the center position, and the rear axle steering controller sends a signal to return the electronically controlled steering rear axle to the center position. The electronically controlled steering rear axle returns to the steering center position according to the signal sent by the rear axle steering controller; when the vehicle speed increases and reaches a certain critical vehicle speed V criti_0 When the steering angle of the 1st axis as the steering reference exceeds the range of (-δ0, δ0), the rear axle steering controller can determine that the current vehicle does not have the conditions for the electronically controlled rear axle to return to the neutral position, and the rear axle steering controller does not send a signal to return the electronically controlled steering rear axle to the neutral position, but sends a signal to continue steering in the previous state of the electronically controlled steering rear axle; when the vehicle speed decreases and reaches a certain critical vehicle speed V criti_1 When the steering angle of the 1st axis as the steering reference is within a small turning angle range (-δ0, δ0), the rear axle steering controller can determine that the current vehicle has the conditions for electronically controlled rear axle steering, and the rear axle steering controller sends a signal to steer the electronically controlled rear axle, and the electronically controlled rear axle performs the steering action according to the signal sent by the rear axle steering controller; when the vehicle speed decreases and reaches a certain critical vehicle speed V criti_1 When the 1-axis steering angle serving as the steering reference exceeds the range of (-δ0, δ0), the rear axle steering controller can determine that the current vehicle does not have the conditions for electronically controlled rear axle steering. The rear axle steering controller does not send a signal to steer the electronically controlled rear axle, but instead sends a signal to keep the previous state of the electronically controlled rear axle in the middle position.

[0023] Furthermore, it also includes a body controller, a vehicle speed sensor, a vehicle speed calculation module and a steering calculation module.

[0024] The vehicle body controller stores the vehicle acceleration a at each gear of the gearbox and the typical engine speed;

[0025] The vehicle speed calculation module, the body controller determines the current theoretical vehicle speed V according to the function V1 = f(V0, a, Δt). 1_theory , where V0 is the vehicle speed at the previous moment, a is the vehicle acceleration value at the current gear and current engine speed, and Δt is the calculation period;

[0026] The vehicle body controller receives the current vehicle speed signal V1 transmitted by the vehicle speed sensor;

[0027] The vehicle body controller compares the current theoretical vehicle speed V 1_theory and V1;

[0028] When ΔV=V1-V 1_theory At a certain set threshold (-ΔV criti , ΔV criti ), the body controller determines that the current vehicle speed is normal, and sends V1 to the steering calculation module;

[0029] When ΔV=V1-V 1_theory Exceeds a certain threshold ΔV criti When the vehicle body controller determines that the current vehicle speed may be abnormal, the vehicle body controller sends V to the steering calculation module. 1_theory ;

[0030] The steering calculation module receives the vehicle speed signal transmitted by the vehicle speed calculation module and controls the steering of the electronically controlled rear axle.

[0031] The present invention provides a control method for a rear axle steering system with pressure shock protection, comprising the following steps:

[0032] The rear axle steering controller obtains vehicle speed, 1st axle steering angle, and electronically controlled axle steering angle information;

[0033] When the vehicle speed increases and reaches a certain critical speed V criti_0 When the 1-axis steering angle used as the steering reference is within a certain small angle range (-δ0, δ0), the rear axle steering controller can determine that the current vehicle has the conditions for the electronically controlled rear axle to return to the center position, and the rear axle steering controller sends a signal to return the electronically controlled steering rear axle to the center position. The electronically controlled steering rear axle returns to the steering center position according to the signal sent by the rear axle steering controller, otherwise the next step is executed;

[0034] When the vehicle speed increases and reaches a certain critical speed V criti_0 When the 1-axis steering angle used as the steering reference exceeds the range of (-δ0, δ0), the rear axle steering controller can determine that the current vehicle does not have the conditions for the electronically controlled rear axle to be steered back to the neutral position, and the rear axle steering controller does not send a signal to return the electronically controlled steering rear axle to the neutral position, but sends a signal to allow the electronically controlled steering rear axle to continue steering in the previous state;

[0035] When the vehicle speed decreases and reaches a certain critical speed V criti_1 When the 1-axis steering angle used as the steering reference is within a small angle range (-δ0, δ0), the rear axle steering controller can determine that the current vehicle has the conditions for electronically controlled rear axle steering, and the rear axle steering controller sends a signal to steer the electronically controlled rear axle, and the electronically controlled rear axle performs the steering action according to the signal sent by the rear axle steering controller, otherwise, the next step is executed;

[0036] When the vehicle speed decreases and reaches a certain critical speed V criti_1 When the 1-axis steering angle serving as the steering reference exceeds the range of (-δ0, δ0), the rear axle steering controller can determine that the current vehicle does not have the conditions for electronically controlled rear axle steering. The rear axle steering controller does not send a signal to steer the electronically controlled rear axle, but instead sends a signal to keep the previous state of the electronically controlled rear axle in the middle position.

[0037] The following steps are also included:

[0038] The vehicle body controller stores the vehicle acceleration a at each gear of the gearbox and the typical engine speed;

[0039] The vehicle speed calculation module, the body controller determines the current theoretical vehicle speed V according to the function V1 = f(V0, a, Δt). 1_theory , where V0 is the vehicle speed at the previous moment, a is the vehicle acceleration value at the current gear and current engine speed, and Δt is the calculation period;

[0040] The vehicle body controller receives the current vehicle speed signal V1 transmitted by the vehicle speed sensor;

[0041] The vehicle body controller compares the current theoretical vehicle speed V 1_theory and V1;

[0042] When ΔV=V1-V 1_theory At a certain set threshold (-ΔV criti , ΔV criti ), the body controller determines that the current vehicle speed is normal, and sends V1 to the steering calculation module;

[0043] When ΔV=V1-V 1_theory Exceeds a certain threshold ΔV criti When the vehicle body controller determines that the current vehicle speed may be abnormal, the vehicle body controller sends V to the steering calculation module. 1_theory ;

[0044] The steering calculation module receives the vehicle speed signal transmitted by the vehicle speed calculation module and controls the steering of the electronically controlled rear axle.

[0045] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0046] (1) The present invention increases the rigidity of the rear axle steering system by adding a back pressure valve between the oil return port T of the proportional valve and the system oil return or the hydraulic oil tank oil return, thereby improving the steering stability of the vehicle when turning on a curve, and avoiding the tail swing problem caused by excessive steering of the rear axle when the vehicle turns rapidly at high speed and heavy load;

[0047] (2) The present invention increases the steering mid-position judgment for the rear axle steering to determine whether the rear wheel is turning or returning to the mid-position, improves the judgment method for locking and unlocking the rear axle in the mid-to-high speed steering mid-position, and increases the vehicle speed calculation module to determine whether the vehicle speed signal is normal. The vehicle speed calculation module is used to solve the problem of rear axle steering loss of control caused by the sudden change in vehicle speed due to the side slip of the driving wheel, thereby improving the steering stability of the vehicle when driving on a curve, ensuring safe steering and driving, and avoiding driving hazards such as drifting or tail swinging caused by improper rear wheel steering control. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 This is a hydraulic principle diagram of the steering valve group in Example 1 of the present invention;

[0049] Figure 2 This is a schematic diagram of the working state of the steering valve group in Example 1 of the present invention;

[0050] Figure 3 This is a hydraulic principle diagram of the steering valve group in Example 2 of the present invention;

[0051] Figure 4 It is a schematic diagram of the flow chart of the rear axle steering controller in the present invention;

[0052] Figure 5 It is a schematic diagram of calculating the equivalent vehicle speed in the vehicle speed calculation module of the present invention;

[0053] Figure 6 It is a control schematic diagram of the vehicle speed calculation module in the present invention;

[0054] Figure 7 It is a flow chart of the vehicle speed calculation module in the present invention. DETAILED DESCRIPTION

[0055] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0056] It should be understood that the present invention can be implemented in different forms and should not be construed as being limited to the embodiments set forth herein. On the contrary, providing these embodiments will make the disclosure thorough and complete and fully convey the scope of the present invention to those skilled in the art. In the accompanying drawings, the sizes and relative sizes of the components may be exaggerated for clarity. The same reference numerals throughout represent the same components.

[0057] Example 1

[0058] like Figure 1 As shown, a rear axle steering system with pressure shock prevention of the present invention comprises a proportional valve 1, a back pressure valve 2, a left steering oil cylinder 3, a right steering oil cylinder 4, a left tire 5a, a right tire 5b, a first overflow valve 6a, a second overflow valve 6b, a third check valve 7a, a fourth check valve 7b, a pressure compensation valve 8, a throttle valve 9, a wheel shaft 10, a left swing arm 11a, a right swing arm 11b, a parallel link 12, a rear axle steering controller, a vehicle body controller, a vehicle speed sensor, a vehicle speed calculation module and a steering calculation module. The left tire 5a and the right tire 5b are symmetrically arranged, and the left tire 5a and the right tire 5b are respectively hinged at both ends of the wheel shaft 10, one end of the wheel shaft 10 is connected to one end of the parallel link 12 through the left swing arm 11a, and the other end of the wheel shaft 10 is connected to the other end of the parallel link 12 through the right swing arm 11b. One end of the left steering cylinder 3 is hinged to the wheel axle 10, and the other end of the left steering cylinder 3 is hinged to the middle of the left swing arm 11a. The left steering cylinder 3 is used to output hydraulic power to drive the left tire to rotate. One end of the right steering cylinder 4 is hinged to the wheel axle 10, and the other end of the right steering cylinder 4 is hinged to the middle of the right swing arm 11b. The right steering cylinder 4 is used to output hydraulic power to drive the left tire to rotate.

[0059] The steering valve group has a working oil port A, a working oil port B, an oil inlet P and an oil return port T. The oil inlet P of the steering valve group is connected to the pressure oil source, and the oil return port T of the steering valve group is connected to the system return oil or the oil return port of the hydraulic oil tank. The working oil port A and the working oil port B of the steering valve group are respectively connected to the left steering cylinder 3 and the right steering cylinder 4 of the vehicle, and are used to control the extension and retraction of the left steering cylinder and the right steering cylinder. The steering valve group includes a proportional valve 1 and a back pressure valve 2 having a working oil port A1, a working oil port B1, an oil inlet P1 and an oil return port T1, wherein the working oil port A1 is communicated with the working oil port A, the working oil port B1 is communicated with the working oil port B, the oil inlet P1 is communicated with the oil inlet P, and the oil return port T1 is communicated with the oil return port T through the back pressure valve 2; the back pressure valve 2 is composed of a first check valve 2a and a second check valve 2b connected in parallel, and the opening pressure of the first check valve 2a is greater than that of the second check valve 2b; wherein the oil inlet of the first check valve 2a is communicated with the oil return port T1 of the proportional valve, and the return oil of the proportional valve returns to the hydraulic oil tank through the first check valve; the oil inlet of the second check valve 2b is communicated with the oil return port T of the steering valve group, and the return oil of the hydraulic oil tank replenishes oil to the oil return chamber of the proportional valve through the second check valve to avoid vacuum.

[0060] For example, when a multi-axle heavy-loaded vehicle turns sharply, due to the lateral acceleration If a certain threshold is exceeded, the rear axle may oversteer under the centrifugal force of the vehicle body, that is, the actual phenomenon of the rear axle is: the actual steering angle of the rear axle exceeds the theoretical steering angle determined by the Akerman theorem. Oversteering will cause the vehicle to drift, and in serious cases, may cause safety accidents. In the present invention, the opening pressure of the first one-way valve 2a acts on the oil return chamber of the proportional valve, that is, the oil return chamber of the left steering cylinder and the right steering cylinder always returns a certain back pressure p0, and the oil return chamber can output a certain amount of force: This force F0 can just balance the lateral force acting on the rear axle, so that the rear axle will not oversteer when the left tire 5a or the right tire 5b turns left or right, and the vehicle will not tail-swing, thereby improving the vehicle's steering safety and handling stability.

[0061] A pressure compensation valve 8 is connected in series between the oil inlet P1 of the proportional valve 1 and the oil inlet P of the steering valve group, and a throttle valve 9 is connected in series between the flow feedback oil port of the pressure compensation valve and the oil inlet P1 of the proportional valve. A first relief valve 6a and a third check valve 7a are connected in sequence between the working oil port A1 of the proportional valve and the working oil port A of the steering valve group, and a second relief valve 6b and a fourth check valve 7b are connected in sequence between the working oil port B1 of the proportional valve and the working oil port B of the steering valve group.

[0062] like Figure 2As shown, the working process of the present invention is as follows: when the end a of the proportional valve is energized, the pressure oil source is connected to the working oil port A of the steering valve group through the oil inlet P of the steering valve group; the working oil port B of the steering valve group is connected to the return oil port T through the proportional valve and the first non-return valve 2a; the working oil port A of the steering valve group is connected to the working chamber 3a of the left steering oil cylinder 3 and the working chamber 4a of the right steering oil cylinder 4 through the hydraulic pipeline; the working oil port B of the steering valve group is connected to the working chamber 3b of the left steering oil cylinder 3 and the working chamber 4b of the right steering oil cylinder 4 through the hydraulic pipeline; the left tire 5a and the right tire 5b are realized under the action of the hydraulic boost output from the working chamber 3a of the left steering oil cylinder and the working chamber 4a of the right steering oil cylinder Figure 2 Here, the second one-way valve 2b can be used to replenish oil to the working chamber 3b and the working chamber 4b.

[0063] In order to further improve the safety and handling stability of rear axle steering and avoid the vehicle swing caused by rear axle steering or neutral locking, the present invention is mainly used to avoid the sudden swing caused by rear axle neutral locking or steering unlocking when driving at high speed. For example, when the vehicle is in the process of turning and the rear axle is also involved in the turning process, and the vehicle speed increases and reaches the set threshold, theoretically the steering controller sends an instruction to turn the rear axle back to the neutral position, and the rear axle is forced to return from a certain turning position to the turning neutral position. Due to the high speed, the change of the rear axle angle will bring about a change in the body posture, which will affect driving safety and handling stability. Similarly, when the vehicle is in the process of turning, the rear axle is kept in the turning neutral position according to the pre-set program. When the vehicle speed decreases and reaches the set threshold, theoretically the rear axle steering controller sends an instruction to turn the rear axle, and the rear axle turns from the turning neutral position according to the pre-set turning angle relationship of the program. Similarly, the change of the rear axle angle will bring about a change in the body posture, which will affect driving safety and handling stability.

[0064] The rear axle steering controller obtains the vehicle speed, the steering angle of the first axle, and the steering angle of the electronically controlled axle. When the vehicle speed increases and reaches a certain critical speed V criti_0 When the steering angle of the 1st axis as the steering reference is within a small turning angle range (-δ0, δ0), the rear axle steering controller can determine that the current vehicle has the conditions for the electronically controlled rear axle to return to the center position, and the rear axle steering controller sends a signal to return the electronically controlled steering rear axle to the center position. The electronically controlled steering rear axle returns to the steering center position according to the signal sent by the rear axle steering controller; when the vehicle speed increases and reaches a certain critical vehicle speed V criti_0 When the steering angle of the 1st axis as the steering reference exceeds the range of (-δ0, δ0), the rear axle steering controller can determine that the current vehicle does not have the conditions for the electronically controlled rear axle to return to the neutral position, and the rear axle steering controller does not send a signal to return the electronically controlled steering rear axle to the neutral position, but sends a signal to continue steering in the previous state of the electronically controlled steering rear axle; when the vehicle speed decreases and reaches a certain critical vehicle speed Vcriti_1 When the steering angle of the 1st axis as the steering reference is within a small turning angle range (-δ0, δ0), the rear axle steering controller can determine that the current vehicle has the conditions for electronically controlled rear axle steering, and the rear axle steering controller sends a signal to steer the electronically controlled rear axle, and the electronically controlled rear axle performs the steering action according to the signal sent by the rear axle steering controller; when the vehicle speed decreases and reaches a certain critical vehicle speed V criti_1 When the 1-axis steering angle serving as the steering reference exceeds the range of (-δ0, δ0), the rear axle steering controller can determine that the current vehicle does not have the conditions for electronically controlled rear axle steering. The rear axle steering controller does not send a signal to steer the electronically controlled rear axle, but instead sends a signal to keep the previous state of the electronically controlled rear axle in the middle position.

[0065] In the above scheme, the vehicle speed signal is an important input signal in the rear axle steering system. If the vehicle speed signal suddenly increases, the rear axle may suddenly change its turning angle. If the vehicle is turning, due to the serious roll of one side of the vehicle, a certain driving wheel slips and the speed increases. If the vehicle speed signal is collected by ABS and converted according to the formula v = r·ω = r·2πn, the speed n increases suddenly, and the vehicle speed v also increases suddenly. The rear axle will follow the vehicle speed input signal according to the angle relationship pre-set by the program. For example, when the vehicle is turning, due to the sudden increase in speed caused by the sudden slip of a certain driving wheel, the vehicle speed signal also rises to a certain value in a very short time. This speed value is just in the speed range pre-set in the steering control program to allow a certain rear axle or several rear axles to turn back to the middle position. Therefore, the rear axle returns to the middle position from a certain steering position in a very short time according to the angle relationship pre-set by the program. The change of the rear axle angle will inevitably bring about a change in the body posture, affecting driving safety and handling stability.

[0066] In order to prevent the rear wheel steering control from losing control due to the sudden change of vehicle speed caused by the side slip, the vehicle body controller pre-stores the vehicle acceleration a at each gear of the gearbox and the typical engine speed;

[0067] The vehicle speed calculation module, the body controller determines the current theoretical vehicle speed V according to the function V1 = f(V0, a, Δt). 1_theory , where V0 is the vehicle speed at the previous moment, a is the vehicle acceleration value at the current gear and current engine speed, and Δt is the calculation period;

[0068] The vehicle body controller receives the current vehicle speed signal V1 transmitted by the vehicle speed sensor;

[0069] The vehicle body controller compares the current theoretical vehicle speed V 1_theory and V1;

[0070] When ΔV=V1-V 1_theoryAt a certain set threshold (-ΔV criti , ΔV criti ), the body controller determines that the current vehicle speed is normal, and sends V1 to the steering calculation module;

[0071] When ΔV=V1-V 1_theory Exceeds a certain threshold ΔV criti When the vehicle body controller determines that the current vehicle speed may be abnormal, the vehicle body controller sends V to the steering calculation module. 1_theory ;

[0072] The steering calculation module receives the vehicle speed signal transmitted by the vehicle speed calculation module and controls the steering of the electronically controlled rear axle.

[0073] like Figure 4 As shown, a control method of a rear axle steering system with pressure shock protection according to the present invention comprises the following steps:

[0074] 101. The rear axle steering controller obtains vehicle speed, 1st axle steering angle, and electronically controlled axle steering angle information;

[0075] 102. When the vehicle speed increases and reaches a certain critical speed V criti_0 When the 1-axis steering angle used as the steering reference is within a certain small angle range (-δ0, δ0), the rear axle steering controller can determine that the current vehicle has the conditions for the electronically controlled rear axle to return to the center position, and the rear axle steering controller sends a signal to return the electronically controlled steering rear axle to the center position. The electronically controlled steering rear axle returns to the steering center position according to the signal sent by the rear axle steering controller, otherwise the next step is executed;

[0076] 103. When the vehicle speed increases and reaches a certain critical speed V criti_0 When the 1-axis steering angle used as the steering reference exceeds the range of (-δ0, δ0), the rear axle steering controller can determine that the current vehicle does not have the conditions for the electronically controlled rear axle to be steered back to the neutral position, and the rear axle steering controller does not send a signal to return the electronically controlled steering rear axle to the neutral position, but sends a signal to allow the electronically controlled steering rear axle to continue steering in the previous state;

[0077] 104. When the vehicle speed decreases and reaches a certain critical speed V criti_1 When the 1-axis steering angle used as the steering reference is within a small angle range (-δ0, δ0), the rear axle steering controller can determine that the current vehicle has the conditions for electronically controlled rear axle steering, and the rear axle steering controller sends a signal to steer the electronically controlled rear axle, and the electronically controlled rear axle performs the steering action according to the signal sent by the rear axle steering controller, otherwise, the next step is executed;

[0078] 105. When the vehicle speed decreases and reaches a certain critical speed V criti_1When the 1-axis steering angle serving as the steering reference exceeds the range of (-δ0, δ0), the rear axle steering controller can determine that the current vehicle does not have the conditions for electronically controlled rear axle steering. The rear axle steering controller does not send a signal to steer the electronically controlled rear axle, but instead sends a signal to keep the previous state of the electronically controlled rear axle in the middle position.

[0079] like Figure 5 , Figure 6 and Figure 7 As shown, the following steps are also included:

[0080] 201. The vehicle body controller stores the vehicle acceleration a at each gear position of the gearbox and the typical engine speed;

[0081] 202, vehicle speed calculation module, the body controller determines the current theoretical vehicle speed V according to the function V1 = f(V0, a, Δt) 1_theory , where V0 is the vehicle speed at the previous moment, a is the vehicle acceleration value at the current gear and current engine speed, and Δt is the calculation period;

[0082] 203. The vehicle body controller receives a current vehicle speed signal V1 transmitted from the vehicle speed sensor;

[0083] 204. The vehicle body controller compares the current theoretical vehicle speed V 1_theory and V1;

[0084] 205. When ΔV=V1-V 1_theory At a certain set threshold (-ΔV criti , ΔV criti ), the body controller determines that the current vehicle speed is normal, and sends V1 to the steering calculation module;

[0085] 206. When ΔV=V1-V 1_theory Exceeds a certain threshold ΔV criti When the vehicle body controller determines that the current vehicle speed may be abnormal, the vehicle body controller sends V to the steering calculation module. 1_theory ;

[0086] 207. The steering calculation module receives the vehicle speed signal transmitted by the vehicle speed calculation module and controls the steering of the electronically controlled rear axle.

[0087] Example 2

[0088] like Figure 3As shown, the structure of embodiment 2 is the same as that of embodiment 1, and the only difference is that the back pressure valve 2 is composed of a relief valve 2c and a check valve 2d in parallel, and the return oil of the proportional valve is returned to the hydraulic oil tank through the relief valve; the oil inlet of the check valve is connected to the return oil port T of the steering valve group, and the return oil of the hydraulic oil tank is replenished to the return oil chamber of the proportional valve through the check valve. Here, the function of the relief valve 2c is the same as that of the first check valve 2a, and the check valve 2d is the same as that of the second check valve 2b.

Claims

1. A rear axle steering system with pressure shock protection, characterized in that: include: The left tire (5a) and the right tire (5b) are symmetrically arranged, The left steering cylinder (3) is used to output hydraulic power to drive the left tire to rotate. The right steering cylinder (4) is used to output hydraulic power to drive the right tire to rotate. A steering valve group having a working oil port A, a working oil port B, an oil inlet P and an oil return port T, the steering valve group comprising a proportional valve (1) having a working oil port A1, a working oil port B1, an oil inlet P1 and an oil return port T1 and a back pressure valve (2), wherein the working oil port A1 is communicated with the working oil port A, the working oil port B1 is communicated with the working oil port B, the oil inlet P1 is communicated with the oil inlet P, and the oil return port T1 is communicated with the oil return port T via the back pressure valve (2); The oil inlet P of the steering valve group is connected to the pressure oil source, the oil return port T of the steering valve group is connected to the system oil return or the oil return port of the hydraulic oil tank, and the working oil port A and the working oil port B of the steering valve group are respectively connected to the left steering cylinder and the right steering cylinder of the vehicle, and are used to control the extension and retraction of the left steering cylinder and the right steering cylinder; The rear axle steering controller is also included. The rear axle steering controller obtains vehicle speed, axle 1 steering angle, and electronically controlled axle steering angle information. When the vehicle speed increases and reaches a certain critical vehicle speed V criti_0 When the steering angle of the 1st axis as the steering reference is within a small turning angle range of [-δ0, δ0], the rear axle steering controller determines that the current vehicle has the conditions for the electronically controlled rear axle to return to the center position, and the rear axle steering controller sends a signal to return the electronically controlled steering rear axle to the center position. The electronically controlled steering rear axle returns to the steering center position according to the signal sent by the rear axle steering controller; when the vehicle speed increases and reaches a certain critical vehicle speed V criti_0 When the 1-axis steering angle used as the steering reference exceeds the range of [-δ0, δ0], the rear axle steering controller determines that the current vehicle does not have the conditions for the electronically controlled rear axle to return to the neutral position, and the rear axle steering controller does not send a signal to return the electronically controlled steering rear axle to the neutral position, but sends a signal to allow the electronically controlled steering rear axle to continue steering in the previous state; when the vehicle speed decreases and reaches a certain critical vehicle speed V criti_1 When the 1-axis steering angle used as the steering reference is within a small angle range of [-δ0, δ0], the rear axle steering controller determines that the current vehicle has the conditions for electronically controlled rear axle steering, and the rear axle steering controller sends a signal to steer the electronically controlled rear axle, and the electronically controlled rear axle performs the steering action according to the signal sent by the rear axle steering controller; when the vehicle speed decreases and reaches a certain critical speed V criti_1 When the 1-axis steering angle serving as the steering reference exceeds the range of [-δ0, δ0], the rear axle steering controller determines that the current vehicle does not have the conditions for electronically controlled rear axle steering, and the rear axle steering controller does not send a signal to steer the electronically controlled rear axle, but instead sends a signal to keep the state before the electronically controlled rear axle steering in the middle position.

2. A rear axle steering system with pressure shock protection according to claim 1, characterized in that: The back pressure valve (2) is composed of a first one-way valve (2a) and a second one-way valve (2b) connected in parallel, wherein the opening pressure of the first one-way valve (2a) is greater than that of the second one-way valve (2b); wherein the oil inlet of the first one-way valve (2a) is connected to the oil return port T1 of the proportional valve, and the oil return of the proportional valve returns to the hydraulic oil tank through the first one-way valve; and the oil inlet of the second one-way valve (2b) is connected to the oil return port T of the steering valve group, and the oil return of the hydraulic oil tank returns to the oil return chamber of the proportional valve through the second one-way valve.

3. The rear axle steering system with pressure shock protection according to claim 1, characterized in that: The back pressure valve (2) is composed of a relief valve (2c) and a check valve (2d) connected in parallel. The return oil of the proportional valve is returned to the hydraulic oil tank through the relief valve. The oil inlet of the check valve is connected to the return oil port T of the steering valve group. The return oil of the hydraulic oil tank is replenished to the return oil chamber of the proportional valve through the check valve.

4. The rear axle steering system with pressure shock protection according to claim 1, characterized in that: A pressure compensation valve (8) is connected in series between the oil inlet P1 of the proportional valve (1) and the oil inlet P of the steering valve group, and a throttle valve (9) is connected in series between the flow feedback oil port of the pressure compensation valve and the oil inlet P1 of the proportional valve.

5. The rear axle steering system with pressure shock protection according to claim 1, characterized in that: A first overflow valve (6a) and a third check valve (7a) are sequentially connected between the working oil port A1 of the proportional valve and the working oil port A of the steering valve group, and a second overflow valve (6b) and a fourth check valve (7b) are sequentially connected between the working oil port B1 of the proportional valve and the working oil port B of the steering valve group.

6. The rear axle steering system with pressure shock protection according to claim 1, characterized in that: The left tire (5a) and the right tire (5b) are respectively hinged to the two ends of the wheel axle (10); the two ends of the wheel axle (10) are respectively connected to the two ends of the parallel connecting rod (12) through a left swing arm (11a) and a right swing arm (11b); one end of the left steering cylinder (3) is hinged to the wheel axle (10); the other end of the left steering cylinder (3) is hinged to the middle of the left swing arm (11a); one end of the right steering cylinder (4) is hinged to the wheel axle (10); the other end of the right steering cylinder (4) is hinged to the middle of the right swing arm (11b).

7. The rear axle steering system with pressure shock protection according to claim 1, characterized in that: It also includes a body controller, a vehicle speed sensor, a vehicle speed calculation module and a steering calculation module. The vehicle body controller stores the vehicle acceleration a at each gear of the gearbox and the typical engine speed; Vehicle speed calculation module, the body controller determines the current theoretical vehicle speed V according to the function V1=f(V0, a, Δt) 1_theory , V0 is the vehicle speed at the previous moment, a is the vehicle acceleration value at the current gear and current engine speed, and Δt is the calculation period; The vehicle body controller receives the current vehicle speed signal V1 transmitted by the vehicle speed sensor; The vehicle body controller compares the current theoretical vehicle speed V 1_theory and V1; When ΔV=V1-V 1_theory At a certain set threshold [-ΔV criti , ΔV criti ], the body controller determines that the current vehicle speed is normal, and sends V1 to the steering calculation module; When ΔV=V1-V 1_theory Exceeds a certain threshold ΔV criti When the vehicle body controller determines that the current vehicle speed is abnormal, the vehicle body controller sends V to the steering calculation module. 1_theory ; The steering calculation module receives the vehicle speed signal transmitted by the vehicle speed calculation module and controls the steering of the electronically controlled rear axle.

8. A control method for a rear axle steering system with pressure shock protection according to any one of claims 1 to 7, characterized in that: The steps include: The rear axle steering controller obtains vehicle speed, 1st axle steering angle, and electronically controlled axle steering angle information; When the vehicle speed increases and reaches a certain critical speed V criti_0 When the 1-axis steering angle used as the steering reference is within a small turning angle range of [-δ0, δ0], the rear axle steering controller determines that the current vehicle has the conditions for the electronically controlled rear axle to be steered back to the center position, and the rear axle steering controller sends a signal to return the electronically controlled steering rear axle to the center position. The electronically controlled steering rear axle returns to the steering center position according to the signal sent by the rear axle steering controller, otherwise the next step is executed; When the vehicle speed increases and reaches a certain critical speed V criti_0 When the 1-axis steering angle used as the steering reference exceeds the range of [-δ0, δ0], the rear axle steering controller determines that the current vehicle does not have the conditions for the electronically controlled rear axle to be steered back to the neutral position, and the rear axle steering controller does not send a signal to return the electronically controlled steering rear axle to the neutral position, but sends a signal to allow the electronically controlled steering rear axle to continue steering in the previous state; When the vehicle speed decreases and reaches a certain critical speed V criti_1 When the 1-axis steering angle used as the steering reference is within a small angle range of [-δ0, δ0], the rear axle steering controller determines that the current vehicle has the conditions for electronically controlled rear axle steering, and the rear axle steering controller sends a signal to steer the electronically controlled rear axle. The electronically controlled rear axle performs the steering action according to the signal sent by the rear axle steering controller, otherwise, the next step is executed; When the vehicle speed decreases and reaches a certain critical speed V criti_1 When the 1-axis steering angle serving as the steering reference exceeds the range of [-δ0, δ0], the rear axle steering controller determines that the current vehicle does not have the conditions for electronically controlled rear axle steering, and the rear axle steering controller does not send a signal to steer the electronically controlled rear axle, but instead sends a signal to keep the state before the electronically controlled rear axle steering in the middle position.

9. The control method of a rear axle steering system with pressure shock protection according to claim 8, characterized in that: The following steps are also included: The vehicle body controller stores the vehicle acceleration a at each gear of the gearbox and the typical engine speed; Vehicle speed calculation module, the body controller determines the current theoretical vehicle speed V according to the function V1=f(V0, a, Δt) 1_theory , V0 is the vehicle speed at the previous moment, a is the vehicle acceleration value at the current gear and current engine speed, and Δt is the calculation period; The vehicle body controller receives the current vehicle speed signal V1 transmitted by the vehicle speed sensor; The vehicle body controller compares the current theoretical vehicle speed V 1_theory and V1; When ΔV=V1-V 1_theory At a certain set threshold [-ΔV criti , ΔV criti ], the body controller determines that the current vehicle speed is normal, and sends V1 to the steering calculation module; When ΔV=V1-V 1_theory Exceeds a certain threshold ΔV criti When the vehicle body controller determines that the current vehicle speed is abnormal, the vehicle body controller sends V to the steering calculation module. 1_theory ; The steering calculation module receives the vehicle speed signal transmitted by the vehicle speed calculation module and controls the steering of the electronically controlled rear axle.

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